Vehicles incorporating automatic transmissions shift automatically between gears in the transmission in response to changes in a throttle input, often associated with adjustments to a linked accelerator pedal. When a driver adjusts the accelerator pedal, these changes affect the throttle input, and in turn results in adjusting automatic transmission operationally connected to an engine and responding to the throttle inputs to find the appropriate gear. There are different types of shifting scenarios including power on/off upshifting and power on/off downshifting. Power On shifting refers to shifting into a higher gear (upshifting) or a lower gear (downshifting) when the accelerator pedal is depressed. Power Off shifting refers to shifting into a higher gear (upshifting) or a lower gear (downshifting) when the accelerator pedal is released.
One form of automatic transmission utilizes a dual clutch in order to shift between gears. In these dual clutch transmissions, there is commonly an off-going clutch that is engaged to and driving the present gear and an on-coming clutch that is used to engage the gear to be shifted into (upshifting or downshifting). Complications in smooth shifting can arise during difficult shifting scenarios. Launch shifting occurs when a vehicle is accelerated from idle and a drive gear shift occurs during the launch itself. When the clutch overheats during a launch or an less than optimum gear is initially selected at launch, a power shift must typically disconnect on off-going gear and activate an on-coming gear. This may result in a torque disturbance to the transmission between the disconnect of the off-going clutch and the re-engagement of the on-coming clutch. This torque disturbance can result in a rough shift and undesirable performance. Similar torque disturbances may result when coming to a stop on a grade with the throttle on and a gear shift is necessitated. In such a situation, while the vehicle is creeping forward it may be necessary to downshift into a lower gear while still powering forward. Again, the disturbance in torque may result in a rough shift and undesirable performance.
It may be desirable for a solution that would reduce the disturbance in transmission torque during power launch shifting situations where environmental conditions or improper gear selection necessitate a gear shift. It would additionally be desirable for a technique that would further reduce transmission torque disturbances during situations where a vehicle may be creeping to a stop on a grade and a change in gear is indicated.